Tuesday, 11 October 2016

More Science from Mrs Avery: Why is water wet?

What does wet mean?
There are 2 answers!
One is about what makes liquids stick to surfaces and 'wet' them - which is to do with forces between molecules.
Why does water feel wet?
When you have water on your clothes or skin, it normally evaporates into the surrounding air. Evaporation produces cooling, because it takes energy. 
Part of the feeling of
wetness is actually coldness.
We feel “wetness” through sensors which sense a mixture of temperature, pressure and the way water feels, then sends this information to our brain telling our brain that water is wet!
Try this
  • Dip your fingers in warm water.

  • Now, try dipping your fingers in other liquids - milk, orange juice or a fizzy drink.

  • Do all the liquids feel wet?

  • Do all the liquids feel the same?

  • What is it about the liquids that feels different?
If we put our hands in water, we feel the water swirl around our fingers and our palms.  We feel the pressure of the water.  Imagine someone squeezes your hand or gives you a strong handshake.  That squeeze is pressure on our hands, but it doesn’t feel wet.  Water gives our hands a very light squeeze, with just a little pressure that changes as our hands move through it. 

Imagine putting your hand into some sand.  You probably have to force the sand out of your way, maybe wiggling your fingers or digging a hole. It’s not easy, like it is with water that just changes shape to let your hand travel through it.  When you take your hand out of the sand, the sand doesn’t go back to its original shape, but water does! The way it moves around our hands is another quality of water that makes us feel wetness.

Most of the time water also feels cool.  It has a cooling effect on our skin. At times it can also be warm. The difference in temperature from the air helps our brain realize that the water isn’t air and that we feel wet.

It is a combination of temperature, pressure and the way it moves tells our brains that water is wet.  Our brains are able to take all this information and figure out what we’re feeling right away!  It’s pretty amazing! 


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